SELECT 
  pfv.variant_id, 
  pfv.position, 
  pfvd.variant 
FROM 
  cscart_product_feature_variants AS pfv 
  INNER JOIN cscart_product_feature_variant_descriptions AS pfvd ON pfv.variant_id = pfvd.variant_id 
  AND pfvd.lang_code = 'en' 
WHERE 
  pfv.variant_id IN (
    9506, 1596, 9503, 1560, 9505, 9510, 1600, 
    9508, 9533, 3037, 9532, 9516, 9531, 
    9534, 9517, 9520, 9530, 2077, 1914, 
    9573, 1674, 9572, 9522, 9588, 9402, 
    1558, 9754, 3442, 9967, 9523, 9895, 
    6360, 9870, 6869, 10066, 9422, 9486, 
    10058, 9627, 9970, 9426
  )

Query time 0.00127

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "43.06"
    },
    "nested_loop": [
      {
        "table": {
          "table_name": "pfv",
          "access_type": "range",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id"
          ],
          "key_length": "3",
          "rows_examined_per_scan": 41,
          "rows_produced_per_join": 41,
          "filtered": "100.00",
          "index_condition": "(`softwarepirmam_hewadelivard_cscart_4`.`pfv`.`variant_id` in (9506,1596,9503,1560,9505,9510,1600,9508,9533,3037,9532,9516,9531,9534,9517,9520,9530,2077,1914,9573,1674,9572,9522,9588,9402,1558,9754,3442,9967,9523,9895,6360,9870,6869,10066,9422,9486,10058,9627,9970,9426))",
          "cost_info": {
            "read_cost": "24.61",
            "eval_cost": "4.10",
            "prefix_cost": "28.71",
            "data_read_per_join": "46K"
          },
          "used_columns": [
            "variant_id",
            "position"
          ]
        }
      },
      {
        "table": {
          "table_name": "pfvd",
          "access_type": "eq_ref",
          "possible_keys": [
            "PRIMARY"
          ],
          "key": "PRIMARY",
          "used_key_parts": [
            "variant_id",
            "lang_code"
          ],
          "key_length": "9",
          "ref": [
            "softwarepirmam_hewadelivard_cscart_4.pfv.variant_id",
            "const"
          ],
          "rows_examined_per_scan": 1,
          "rows_produced_per_join": 41,
          "filtered": "100.00",
          "cost_info": {
            "read_cost": "10.25",
            "eval_cost": "4.10",
            "prefix_cost": "43.06",
            "data_read_per_join": "123K"
          },
          "used_columns": [
            "variant_id",
            "variant",
            "lang_code"
          ]
        }
      }
    ]
  }
}